As a long time Floridian, and one who helped get Rubio elected to the Senate....you are wrong about Rubio being popular in Florida.
The only places Rubio is a little popular is in states other than Florida, only because they know VERY little about him OR they have lots of folks who are in favor of amnesty.
Remember, Donald Trump won the Florida Primary and took every county but 1. Miami/Dade the liberal capitol of the Sunshine state went to the amnesty candidates.
IMO, Rubio as VP will NOT help at all!
That might imply Kasich is a better VP choice, helping to capture OH.
Rubio pulled 660k votes in Florida with 120k in Miami-Dade to 40k for Trump. Moreover Rubio is attractive to young voters and Hispanics. If Trump wants to win Rubio is his bet bet. If he wants to lose he can run with Pat Buchanan.
Actually Broward and Leon counties are much more Democrat voting than Miami-Dade. Otherwise you are spot on. No to Rubio.